In general, suitable surfactants are used as detergents in food processing plants and for washing clothes and dishes in general household. The detergent used is washed away under running water, followed by drying. However, whether the residual detergent (surfactant) exists after drying has not been checked. The impact of the residual detergent on human body has been considered to be one of the factors that cause allergies. A simple method for detecting the presence of the residual detergent has thus been desired.
Japanese Unexamined Patent Application Publication No. 8-320315 describes a method of detecting a surfactant adhering on a surface of a specimen, comprising wiping a test portion of the specimen surface with a detecting medium to transfer the test portion to the detecting medium, bringing the detecting medium into contact with a medium containing a dye, and detecting the surfactant on the basis of changes in color tone of the dye caused by the presence of the surfactant. However, changes in color are often too subtle to identify with naked eye; moreover, the sensitivity has not been satisfactory.
The inventor of the present invention has found that a chemiluminescent liquid emits intense light when brought into contact with trace amounts of residual detergent, and made the present invention on the basis of the further studies.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 8-320315